Recently, there has been considerable interest within the detergent industry to produce modern detergent compositions for flexibility in the ultimate density of the final composition.
Generally, there are three primary types of processes by which detergent granules or powders can be prepared. The first type of process involves spray-drying an aqueous detergent slurry in a spray-drying tower to produce highly porous detergent granules (e.g., tower process for low density detergent compositions). The second type of process involves spray-drying an aqueous detergent slurry in a spray-drying tower as the first step, then, the resultant granules are agglomerated with a binder such as a nonionic or anionic surfactant, finally, various detergent components are dry mixed to produce detergent granules (e.g., tower process plus non-tower [agglomeration] process for high density detergent compositions). In the third type of process, the various detergent components are dry mixed after which they are agglomerated with a binder such as a nonionic or anionic surfactant, to produce high density detergent compositions (e.g., non-tower [agglomeration] process for high density detergent compositions). In the above three processes, the important factors which govern the density of the resulting detergent granules are the shape, porosity and particle size distribution of said granules, the density of the various starting materials, the shape of the various starting materials, and their respective chemical composition.
It is often desirable, for performance reasons, to use a mixture of surfactants. Such surfactants are typically prepared in the form of aqueous pastes (typically 25-70% active). When preparing agglomerated granules from mixtures of such surfactant pastes, there are two approaches generally used. One typical approach is; surfactants in the form of paste are mixed so as to form a co-surfactant paste, followed by agglomerating the paste in a mixer, or in a series of mixers with dry ingredients such as builders (e.g. sodium tripolyphosphate), inorganic fillers (e.g. sodium sulfate), bleaches, etc. This approach is not always desirable in terms of finished product quality. For example, mixing of even a relatively small amount of a non-crystalline surfactant paste, (i.e. the paste of a type of surfactant which is typically sticky and difficult to be applied in an agglomeration process), with a paste of a crystalline surfactant, (i.e. a type which is typically easy to apply in an agglomeration process), results in a co-surfactant paste that has the nature of paste of a non-crystalline surfactant. In other words, this type of approach typically causes stickiness of a co-surfactant paste, when co-surfactants include a non-crystalline surfactant, since such non-crystalline surfactant is generally sticky. Consequently, the granules made by this approach generally include a large amount of undesirable oversized agglomerates. Some reduction in the amount of oversize agglomerates can be achieved by using relatively large amounts of flow aids such as zeolites and silicates in the agglomeration step. This, however results in added expense. Another typical approach is, each type of surfactant is formulated into separate agglomerates and then both agglomerates are blended. This approach typically is not desirable since the cost for the parallel agglomeration is rather expensive.
Accordingly, there remains a need in the art to have a process for producing a detergent composition which reduces the level of resulting undesirable oversized agglomerates, when starting detergent materials include a co-surfactant which is non-crystalline. Also, there remains a need for such a process which is more efficient, flexible and economical to facilitate large-scale production of detergents for flexibility in the ultimate density of the final composition.